Pneumatic solids transfer pump

ABSTRACT

A transfer pump for moving pellets of adhesive includes a pump housing with an adhesive inlet coupled to a supply hopper, an adhesive outlet coupled to an outlet hose, and an adhesive passage extending between the adhesive inlet and the adhesive outlet. A first air nozzle communicates with the adhesive passage adjacent the adhesive inlet and expels a first air jet that pushes pellets of adhesive through the adhesive passage. A second air nozzle communicates with the adhesive passage between the adhesive inlet and the adhesive outlet and expels a plurality of second air jets that draw pellets of adhesive through the adhesive passage by a vacuum force. The first and second air nozzles prevent clogging of pellets in the adhesive passage and enable movement of larger pellets than either air nozzle individually.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/637,986, filed on Apr. 25, 2012 (pending), thedisclosure of which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to a transfer pump for solidmaterials and more particularly, to a transfer pump for moving adhesivepellets from a supply hopper to an adhesive melter.

BACKGROUND

In adhesive dispensing systems, a dispensing module is generally fedliquid adhesive material from an adhesive melter or another similarsupply device. These adhesive melters receive a controlled supply ofsolid adhesive material in the form of pellets from a supply hopper orsome other storage unit. In this regard, transfer pumps for solidmaterials are used to control the supply of pellets of adhesive from thesupply hopper to the adhesive melter. More particularly, transfer pumpsremove pellets of adhesive from the supply hopper and force the pelletsof adhesive with pressurized air through an outlet hose and to theadhesive melter, where the pellets of adhesive are melted to a liquidstate for delivery to the dispensing module. The pellets of adhesiveutilized in these adhesive dispensing systems have various shapes andsizes, but conventional transfer pumps are limited in what size andshape of pellets can be moved through the outlet hose to the adhesivemelter.

In one example of a transfer pump known as a Venturi pump, the transferpump expels one or more air jets through a passage to form a vacuumforce that draws pellets of adhesive from the supply hopper and throughthe transfer pump. However, Venturi pumps are generally limited tocreating a vacuum force of up to one atmosphere, thereby limiting thesize of pellets that may be effectively drawn through the transfer pump.Additionally, the passage through which the air jets are expelled mustbe designed with a narrowed throat portion carefully tailored tomaximize the vacuum force produced by the Venturi pump. The diameter ofthis narrowed throat portion may constrict or clog flow of pellets ofadhesive through the transfer pump, thereby limiting the maximum size ofpellets of adhesive that are moveable with the air jets.

In another example of a transfer pump known as a gravity eductor, thetransfer pump expels an air jet to push pellets of adhesive from aninlet of the transfer pump and through the transfer pump. The pellets ofadhesive are gravity fed into the inlet of the transfer pump by thesupply hopper. Although the force exerted by the air jet in a gravityeductor can move a large number of larger pellets of adhesive, theresultant higher density of material within the transfer pump may clogthe transfer pump, especially when the air jet is stopped and thenrestarted. As a result, gravity eductor transfer pumps cannot be stoppedduring operation unless the supply hopper feeding the gravity eductor isempty or the supply hopper includes additional valve structure forcutting off the gravity feed of pellets into the transfer pump. Thisadditional valve structure is expensive and complicated, so most gravityeductors do not include the valve structure and are thus not stoppeduntil the supply hopper is empty.

Consequently, it would be desirable to address these and other concernsassociated with conventional transfer pumps.

SUMMARY OF THE INVENTION

In one embodiment of the current invention, a transfer pump isconfigured to move pellets of adhesive from a supply hopper to anadhesive melter. The transfer pump includes a pump housing with anadhesive inlet configured to receive pellets of adhesive from the supplyhopper, an adhesive outlet configured to be coupled to an outlet hoseleading to the adhesive melter, and an adhesive passage extendingbetween the adhesive inlet and the adhesive outlet. The adhesive passagedefines a passage axis and a passage periphery. The transfer pump alsoincludes a first air nozzle communicating with the adhesive passageadjacent the adhesive inlet. The first air nozzle is configured to expela first air jet in a direction generally along the passage axis to pushpellets of adhesive through the adhesive passage. The transfer pumpfurther includes a second air nozzle communicating with the adhesivepassage between the adhesive inlet and the adhesive outlet. The secondair nozzle is configured to expel a plurality of second air jets in adirection generally along the passage periphery to generate a vacuumforce at the adhesive inlet that draws pellets of adhesive through theadhesive passage.

In one aspect, the adhesive inlet receives pellets of adhesive bygravity feed from the supply hopper. As a result, the first air nozzleoperates as a gravity eductor for transferring pellets of adhesive tothe adhesive outlet. In another aspect, the adhesive passage includes athroat portion with a narrowing inner diameter, and the plurality ofsecond air jets is directed generally tangential to the throat portion.Consequently, the second air nozzle operates as a Venturi pump fortransferring pellets of adhesive to the adhesive outlet.

In some embodiments, the transfer pump includes a controller operable tocontrol air supplied to each of the first and second air nozzles. Thecontroller operates the first air nozzle to force pellets of adhesiveout of the adhesive inlet to prevent the pellets from clogging theadhesive inlet. The controller also operates the second air nozzle tothrottle a flow of the pellets through the adhesive passage to preventthe pellets from clogging the adhesive passage or the outlet hose. Whenthe transfer pump is to be stopped, the controller stops air flow to thefirst air nozzle and continues to supply air flow to the second airnozzle for a period of time after stopping air flow to the first airnozzle. The second air nozzle draws any remaining pellets of adhesive inthe pump housing away from the adhesive inlet, and then the controllerstops air flow to the second air nozzle.

The supply hopper and the pump housing collectively define a devicefootprint with a device depth. The pump housing is arranged such thatthe passage axis is angled from a horizontal direction, thereby reducingthe device depth and minimizing the device footprint.

In another embodiment of the invention, a method for transferring solidpellets of adhesive from a supply hopper to an adhesive melter includesreceiving the pellets of adhesive into an adhesive inlet of a pumphousing. The pump housing also includes an adhesive outlet and anadhesive passage defining a passage axis and a passage periphery. Themethod also includes discharging a first air jet from a first air nozzlepositioned adjacent the adhesive inlet. The first air jet is directedgenerally along the passage axis to push the pellets of adhesive fromthe adhesive inlet through the adhesive passage. The method furtherincludes discharging a plurality of second air jets from a second airnozzle positioned between the adhesive inlet and the adhesive outlet.The plurality of second air jets is directed generally along the passageperiphery to generate a vacuum force at the adhesive inlet and draw thepellets of adhesive through the adhesive passage.

These and other objects and advantages of the invention will become morereadily apparent during the following detailed description taken inconjunction with the drawings herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with the general description of the invention given above andthe detailed description of the embodiments given below, serve toexplain the principles of the invention.

FIG. 1 is a perspective view of an adhesive dispensing system includinga supply hopper and a transfer pump.

FIG. 2 is a perspective view of the supply hopper and transfer pump ofFIG. 1 with the device housing shown in phantom.

FIG. 3 is a cross-sectional side view of the supply hopper and transferpump of FIG. 1 along line 3-3, with the supply hopper empty.

FIG. 4 is a cross-sectional side view of the supply hopper and transferpump of FIG. 3, with the transfer pump moving pea-shaped pellets ofadhesive from the supply hopper in a first operational state.

FIG. 5 is a cross-sectional side view of the supply hopper and transferpump of FIG. 4, with the transfer pump removing pea-shaped pellets ofadhesive from the transfer pump in a second operational state.

FIG. 6 is a cross-sectional side view of the supply hopper and transferpump of FIG. 3, with the transfer pump moving slat-shaped pellets ofadhesive from the supply hopper in a first operational state.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

FIGS. 1-6 illustrate an adhesive dispensing system 10 including a supplyhopper 12 and a pneumatic solids transfer pump 14 according to oneembodiment of the current invention. As shown in FIG. 1, the transferpump 14 is configured to move solid pellets of adhesive (not shown) oranother solid material from the supply hopper 12 into an adhesive melter16. The solid material may define any form or shape that is convenientfor delivering and melting by the adhesive melter 16; however pelletshave been chosen for illustrative purposes in the illustratedembodiment. After the solid pellets of adhesive are melted by theadhesive melter 16, the now-liquefied adhesive is applied to a substrateby an adhesive dispensing module 18 as well understood in the dispensingart. As a result, the transfer pump 14 assists in controlling the amountof adhesive delivered to the adhesive melter 16 and to the adhesivedispensing module 18. As described in further detail below, the transferpump 14 advantageously includes two air nozzles that collectivelyoperate to move larger pellets of adhesive to the adhesive melter 16than either air nozzle would individually.

With reference to FIGS. 1 and 2, the supply hopper 12 and the transferpump 14 are partially contained within a device housing 20 of desirableshape and properties. For example, the device housing 20 as shown isgenerally a rectilinear box that may isolate portions of the supplyhopper 12 and the transfer pump 14 from environmental interference. Itwould be understood that other configurations of the device housing 20are possible in other embodiments within the scope of the invention. Byway of example, the device housing 20 may include handles, wheels, alid, or any other combination of features intended to enhance theoperation of the supply hopper 12 and the transfer pump 14.

FIG. 2 shows a view of the supply hopper 12 and the transfer pump 14with portions of the device housing 20 shown in phantom. Moreparticularly, the supply hopper 12 includes a funnel portion 22 and acollector portion 24 extending between the funnel portion 22 and thetransfer pump 14. The funnel portion 22 is defined by a plurality ofhopper sidewalls 26 (four shown in the exemplary embodiment) eachtapering inwardly towards the collector portion 24. Thus, pellets ofadhesive (not shown) are fed by gravity from a hopper opening 28 at thetop of the funnel portion 22 into the collector portion 24 and thetransfer pump 14. It will be understood that the supply hopper 12 may bemodified in other embodiments to gravity feed a metered supply ofpellets of adhesive. The collector portion 24 defines a curved profilebetween the hopper portion 22 and the transfer pump 14 for reasons setforth in greater detail below. As shown in FIG. 2, the device housing 20of the exemplary embodiment also includes support ribs 30 formaintaining the supply hopper 12 in position within the device housing20. It will be appreciated that these support ribs 30 may be omitted inother embodiments, and the overall shape of the supply hopper 12 mayalso be modified in other embodiments consistent with the scope of theinvention.

With continued reference to FIGS. 2 and 3, the transfer pump 14 includesa pump housing 32. The pump housing 32 further includes an adhesiveinlet 34, an adhesive outlet 36, and an adhesive passage 38 extendingbetween the adhesive inlet 34 and the adhesive outlet 36. The adhesiveinlet 34 is coupled to the supply hopper 12 at the collector portion 24for gravity feeding the pellets into the pump housing 32. The adhesiveoutlet 36 defines a connection socket 40 configured to receive an outlethose 42 leading to the adhesive melter 16. The transfer pump 14therefore actuates movement of pellets of adhesive from the adhesiveinlet 34 through the adhesive passage 38, the adhesive outlet 36, andthe outlet hose 42 to the adhesive melter 16 during operation of thetransfer pump 14. The pump housing 32 also includes a first air inletport 44 and a second air inlet port 46 operatively connected tocorresponding first and second air nozzles 48, 50 as described infurther detail below. The first air inlet port 44 is connected to afirst pressurized air supply 52 and the second air inlet port 46 isconnected to a second pressurized air supply 54 as shown in FIG. 2. Itwill be understood that the first and second pressurized air supplies52, 54 may be a single pressurized air source in some embodiments of theinvention. The transfer pump 14 also includes a controller 56 forcontrolling the air flow delivered to each of the first and second airinlet ports 44, 46 from the first and second pressurized air supplies52, 54.

The adhesive passage 38 is more clearly shown in FIG. 3. In this regard,the adhesive passage 38 defines a passage axis 60 and a passageperiphery 62 surrounding the passage axis 60. As described above, thecollector portion 24 of the supply hopper 12 has a curved profile sothat the passage axis 60 is angled upwardly from a horizontalorientation by an angle a. As a result, a total device depth D definedby the supply hopper 12 and the transfer pump 14 is reduced from whatthe depth D would be if the passage axis 60 were horizontal. To thisend, a device footprint 64 (shown in FIG. 2) defined by the supplyhopper 12 and the transfer pump 14 is minimized by angling the transferpump 14 and the passage axis 60 upwardly. It will be understood that thedevice depth D and the device footprint 64 may be modified by changingthe angle a without departing from the scope of the invention, butminimizing the device footprint 64 is generally desirable to save spacein working environments.

With continued reference to FIG. 3, the adhesive inlet 34 of the pumphousing 32 tapers inwardly towards the adhesive passage 38 to collectpellets of adhesive fed through the collector portion 24 of the supplyhopper 12. The first air nozzle 48 is located just upstream of theadhesive inlet 34 within the collector portion 24 for pushing pellets ofadhesive into and through the adhesive passage 38. The adhesive passage38 further includes a throat portion 66 in which the passage periphery62 has a narrowed inner diameter θ from the remainder of the adhesivepassage 38. In order to avoid the formation of sharp shoulders wherepellets of adhesive could catch during movement through the transferpump 14, the throat portion 66 is bounded by a converging portion 68facing towards the adhesive inlet 34 and a diverging portion 70 facingtowards the adhesive outlet 70. The throat portion 66 reduces thepressure of air flow through the pump housing 32 to assist with theformation of a vacuum force as described in further detail below. Thesecond air nozzle 50 is located between the adhesive inlet 34 and theadhesive outlet 38, and more particularly, between the adhesive inlet 34and the converging portion 68. The diverging portion 70 is shownextending all the way from the throat portion 66 to the connectionoutlet 40 for the outlet hose 42, although it will be understood thatthe diverging portion 70 may be shortened in length in other embodimentsconsistent with the scope of the invention.

It will be understood that each of the first and second air nozzles 48,50 inherently generates a vacuum force upstream of the air nozzles 48,50 when pressurized air is discharged from the air nozzles 48, 50 tomove pellets of adhesive as described in further detail below. In orderto move larger pellets of adhesive through the transfer pump 14, thenarrowed inner diameter θ of the throat portion 66 must be enlarged toprevent constriction or clogging of pellets in that throat portion 66.However, as the narrowed inner diameter θ is enlarged from an idealVenturi size to approach the larger diameters of the adhesive passage 38at the converging portion 68 and the diverging portion 70, the vacuumforce that can be generated by the second air nozzle 50 is reducedsignificantly. As a result, increasing the size of the throat portion 66reduces the ability of the second air nozzle 50 to move pellets ofadhesive. Thus, the transfer pump 14 advantageously includes the firstair nozzle 48 to overcome the reduction in vacuum force produced by thesecond air nozzle 50 when the throat portion 66 includes a largerdiameter θ as shown in FIG. 3.

Turning to FIGS. 4-6, the transfer pump 14 is shown in operation withtwo different types of pellets 72, 74 of adhesive. The pellets 72, 74are propelled through the adhesive inlet 34 and the adhesive passage 38by pneumatic forces formed by air flow expelled by the first air nozzle48 and the second air nozzle 50. As described above, the first airnozzle 48 and the second air nozzle 50 receive pressurized air from thefirst air supply 52 and second air supply 54, respectively. In thisregard, the pump housing 32 includes a first air passage 76 extendingbetween the first air nozzle 48 and the first air inlet port 44 todeliver air from the first air supply 52 to the first air nozzle 48 whenthe first air nozzle 48 is active. Similarly, the pump housing 32 alsoincludes a second air passage 78 in the form of an annular air chamber78 extending between the second air nozzle 50 and the second air inletport 46 to deliver air from the second air supply 54 to the second airnozzle 50 when the second air nozzle 50 is active.

The pellets 72 of adhesive shown in FIGS. 4 and 5 define a spherical orpea-shape, which is generally easier to move with pneumatic forcebecause the pea shape always presents a relatively large surface areafor pressurized air to apply force to the pellet 72. The rounded peashape of the pellets 72 also do not lead to stacking or catching of thepellets 72 within the adhesive passage 38. FIG. 4 shows the transferpump 14 during normal operation with the first air nozzle 48 and thesecond air nozzle 50 both active for moving the pellets 72 through theadhesive passage 38 and the outlet hose 42. The first air nozzle 48 isarranged to expel a first air jet as shown by arrows 80 along thepassage axis 60 similar to a gravity eductor. In this regard, the firstair nozzle 48 is capable of forming positive pressure to push gravityfed pellets 72 out of the adhesive inlet 34 and through the adhesivepassage 38. The first air nozzle 48 also effectively generates a vacuumforce upstream of the first air nozzle 48 to draw pellets 72 from theadhesive inlet 34.

Concurrently, the second air nozzle 50 expels a plurality of second airjets indicated by arrows 82 generally along the passage periphery 62and, more particularly, generally tangential to the throat portion 66 atthe converging portion 68. Because the throat portion 66 is narrowerthan the adhesive inlet 34, the pellets 72 are subject to a Venturieffect in which the pressure of the air flow is lower in the throatportion 66 than at the adhesive inlet 34. This pressure differentialproduces a vacuum force at the adhesive inlet 34 similar to a Venturipump and therefore applies additional force to draw pellets 72 from theadhesive inlet 34 and through the adhesive passage 38. Under theinfluence of the additive pressures of the first air nozzle 48 and thesecond air nozzle 50, the pellets 72 travel through the transfer pump 14and the outlet hose 42 at an upward angle α. To this end, the combinedforces generated by the first air nozzle 48 and the second air nozzle 50reliably actuates movement of larger pellets 72 from the adhesive inlet34 and through the adhesive passage 38 than either of the air nozzles48, 50 could move individually.

In the normal operational state shown in FIG. 4, pellets 72 are fed bygravity from the supply hopper 12 into the adhesive inlet 34, at whichpoint a combined pushing force from the first air jet expelled by thefirst air nozzle 48 and a drawing force from the plurality of second airjets expelled by the second air nozzle 50 cooperate to move thesepellets 72 through the adhesive passage 38 and the outlet hose 42. Thecombination of a pushing force from the first air nozzle 48 and adrawing force from the second air nozzle 50 collectively enables thetransfer pump 14 to reliably move relatively large pellets 72 to theadhesive melter 16 while avoiding clogging at any portion of thetransfer pump 14 or the outlet hose 42. To this end, the first air jetfrom the first air nozzle 48 directly forces pellets 72 out of theadhesive inlet 34 as the pellets 72 fall from the supply hopper 12,thereby preventing clogging of the adhesive inlet 34 with pellets 72.The plurality of second air jets from the second air nozzle 50 operatesto throttle a flow of the pellets 72 through the adhesive passage 38,which prevents the pellets 72 from clogging the adhesive passage 38 orthe outlet hose 42.

In the illustrated embodiment, the first air supply 52 and the secondair supply 54 are separate and independently controlled by thecontroller 56. In this regard, the controller 56 operates to set a flowrate of air expelled from each of the first and second air nozzles 48,50 depending upon the particular type and size of pellet 72 to be movedby the transfer pump 14. However, it will be appreciated that suchcontrol effects may also be achieved with multiple valves or similarlycapable hardware at the pump housing 32 in other embodiments within thescope of the invention. The controller 56 therefore operates the firstand second air nozzles 48, 50 to transfer the pellets 72 without causingclogging as described above.

For example, a typical inner diameter of the outlet hose 42 in theadhesive dispensing setting is about 32 millimeters. The hybrid pushingand drawing forces applied by the transfer pump 14 advantageously enablereliable transfer of pellets 72 having a largest dimension (e.g.,diameter for a spheroid) of up to 15 millimeters without clogging orother failure. By contrast, conventional transfer pumps of the same sizeas described in the background above cannot reliably transfer pelletshaving a largest dimension above 12 millimeters. In this regard, aconventional transfer pump has proven to clog or fail with 15 millimeterpellets at a rate of about 1 out of every 35 cycles, while the transferpump 14 of the current invention successfully transferred 15 millimeterpellets for over 250 successive cycles without failure. Thus, thetransfer pump 14 unexpectedly improves the size of pellets 72 that maybe reliably transferred from the supply hopper 12 to the adhesive melter16.

Moreover, the independent control of the first air nozzle 48 and thesecond air nozzle 50 by the controller 56 also provides additionalbenefits. More specifically, the transfer pump 14 of the currentinvention reduces clogging caused by pellets 72 settling within the pumphousing 32 between operational cycles of the transfer pump 14. Forinstance, the transfer pump 14 may require a shutdown before the supplyhopper 12 is emptied of pellets 72. In such a situation, the pellets 72located in the supply hopper 12 continue to fall by the force of gravityinto the collector portion 24 and into the adhesive inlet 34. If thesepellets 72 remain stagnant at this location, especially in warmoperating environments, the pellets 72 may begin to stick together andclog the adhesive inlet 34. However, the controller 56 is configured toavoid this stagnant collection of pellets 72 in the pump housing 32 byrunning the second air nozzle 50 after shutting off the first air nozzle48.

In this regard, the controller 56 stops air flow to the first air nozzle48 to stop pushing pellets 72 from the collector portion 24 and theadhesive inlet 34. The controller 56 continues to supply air flow to thesecond air nozzle 50 for a period of time after stopping air flow to thefirst air nozzle 48. The plurality of second air jets from the secondair nozzle 50 continues to draw the pellets present within the pumphousing 32 through the adhesive passage 38 and the outlet hose 42.Additionally, the relatively low vacuum pressure generated by the secondair nozzle 50, which is caused by the large diameter θ of the throatportion 66, does not draw additional pellets 72 from the collectorportion 24 into the adhesive inlet 34. Thus, the transfer pump 14 andthe outlet hose 42 are each substantially cleared of pellets 72 as shownin FIG. 5. After the second air nozzle 50 has operated alone for theperiod of time, which may be adjustable or predetermined by thecontroller 56, the air flow to the second air nozzle 50 is stopped untilthe transfer pump 14 is to be activated to the normal operating stateagain. Any small number of pellets 72 that may gather in the collectorportion 24 adjacent to the adhesive inlet 34 is reliably pushed into andthrough the adhesive passage 38 by the first and second air nozzles 48,50 upon the start of a new operational cycle. Consequently, the transferpump 14 advantageously enables starting and stopping of transfer ofpellets 72 before the supply hopper 12 is completely emptied.

Additionally, the transfer pump 14 is operable to reliably move pellets72, 74 of differing shapes and sizes. FIG. 6 illustrates pellets 74 ofadhesive that define a slat shape, also referred to as a thinrectangular box or prism. These slat shaped pellets 74 represent oneworst case scenario because the pellets 74 may rotate to present onlythe thin side for the pressurized air to apply force upon; additionally,the flat sides of the slat shaped pellets 74 enables stacking of thepellets 74 at the formation of “rat holes” within the adhesive passage38. However, the transfer pump 14 of the current invention stillreliably transfers these pellets 74 of adhesive through the adhesivepassage 38 and the outlet hose 42. Similar to the pea-shape pellets 72previously described, slat shaped pellets 74 up to at least 15millimeters in size (e.g., along a longest side edge) are transferred bythe transfer pump 14 without clogging or other failure.

As a result, the transfer pump 14 is subject to less downtime formaintenance and repairs while enabling selective control of how muchsolid adhesive material is delivered to the adhesive melter 16. Thetransfer pump 14 reliably transfers relatively large sized pellets 72,74 in varying shapes with a minimized device footprint 64. In thisregard, the transfer pump 14 of the current invention achieves numerousbenefits in pneumatic powered solids transfer.

While the present invention has been illustrated by a description of anexemplary embodiment, and while this embodiment has been described inconsiderable detail, there is no intention to restrict, or in any waylimit, the scope of the appended claims to such detail. Additionaladvantages and modification will readily appear to those skilled in theart. Therefore, the invention in its broadest aspects is not limited tothe specific detail shown and described. The various features disclosedherein may be used in any combination necessary or desired for aparticular application. Consequently, departures may be made from thedetails described herein without departing from the spirit and scope ofthe claims which follow.

What is claimed is:
 1. A transfer pump configured to move pellets ofadhesive from a supply hopper to an adhesive melter, comprising: a pumphousing including an adhesive inlet configured to receive pellets ofadhesive from the supply hopper, an adhesive outlet configured to becoupled to an outlet hose leading to the adhesive melter, and anadhesive passage located between said adhesive inlet and said adhesiveoutlet, said adhesive passage defining a passage axis and a passageperiphery; a first air nozzle communicating with said adhesive passageadjacent said adhesive inlet and configured to expel a first air jet ina direction generally along said passage axis to push pellets ofadhesive through said adhesive passage; and a second air nozzlecommunicating with said adhesive passage between said adhesive inlet andsaid adhesive outlet, said second air nozzle configured to expel aplurality of second air jets in a direction generally along said passageperiphery to draw pellets of adhesive through said adhesive passage witha vacuum force formed at said adhesive inlet.
 2. The transfer pump ofclaim 1, wherein said adhesive inlet receives pellets of adhesive bygravity feed from the supply hopper such that said first air nozzleoperates as a gravity eductor for transferring pellets of adhesive tosaid adhesive outlet.
 3. The transfer pump of claim 2, wherein saidadhesive passage includes a throat portion including a narrowing innerdiameter, and said plurality of second air jets is directed generallytangential to said throat portion such that said second air nozzleoperates as a Venturi pump for transferring pellets of adhesive to saidadhesive outlet.
 4. The transfer pump of claim 1, further comprising: acontroller operatively coupled to said first and second air nozzles andoperable to control air supplied to each of said first and second airnozzles.
 5. The transfer pump of claim 4, wherein said controlleroperates said first air nozzle to force pellets of adhesive out of saidadhesive inlet to prevent the pellets from clogging said adhesive inlet,and said controller operates said second air nozzle to throttle a flowof the pellets through said adhesive passage to prevent the pellets fromclogging said adhesive passage or the outlet hose.
 6. The transfer pumpof claim 4, wherein said controller is operable to perform the followingsteps when operation of the transfer pump is to be stopped: stopping airflow to said first air nozzle to stop pushing pellets of adhesive fromsaid adhesive inlet; continuing to supply air flow to said second airnozzle for a period of time after stopping air flow to said first airnozzle such that said second air nozzle draws any pellets of adhesiveremaining in said pump housing from said adhesive inlet; and stoppingair flow to said second air nozzle to stop transfer of the pellets ofadhesive to the adhesive melter.
 7. The transfer pump of claim 1,wherein the supply hopper and said pump housing collectively define adevice footprint including a device depth, and said passage axis isangled from a horizontal direction to reduce said device depth andthereby minimize said device footprint.
 8. A method for transferringsolid pellets of adhesive from a supply hopper to an adhesive melter,the method comprising: receiving the pellets of adhesive into anadhesive inlet of a pump housing, the pump housing also including anadhesive outlet and an adhesive passage defining a passage axis and apassage periphery; discharging a first air jet from a first air nozzlepositioned adjacent the adhesive inlet and directed generally along thepassage axis to push the pellets of adhesive from the adhesive inletthrough the adhesive passage; and discharging a plurality of second airjets from a second air nozzle positioned between the adhesive inlet andthe adhesive outlet and directed generally along the passage peripheryto draw the pellets of adhesive through the adhesive passage by a vacuumforce formed at the adhesive inlet.
 9. The method of claim 8, whereinreceiving the pellets of adhesive into the adhesive inlet furthercomprises: feeding the pellets of adhesive into the adhesive inlet usinggravity.
 10. The method of claim 9, wherein the adhesive passage of thepump housing includes a throat portion with a narrowing inner diameter,and discharging the plurality of second air jets further comprises:directing the plurality of second air jets generally tangential to thethroat portion to generate the vacuum force at the adhesive inlet. 11.The method of claim 8, further comprising: controlling the first air jetto force the pellets of adhesive out of the adhesive inlet to therebyprevent clogging of the pellets of adhesive at the adhesive inlet. 12.The method of claim 11, further comprising: controlling the plurality ofsecond air jets to throttle a flow of the pellets of adhesive throughthe adhesive passage, thereby preventing clogging of the pellets ofadhesive at the adhesive passage.
 13. The method of claim 8, furthercomprising: stopping air flow to the first air nozzle to stop pushingthe pellets of adhesive from the adhesive inlet; supplying air flow tothe second air nozzle for a period of time after stopping air flow tothe first air nozzle such that the second air nozzle draws any pelletsof adhesive remaining in the pump housing from the adhesive inlet; andstopping air flow to the second air nozzle to stop transfer of thepellets of adhesive to the adhesive melter.